In our study, the techniques we compare assign suspiciousness scores to different program elements. UniVal assigns scores to numeric, string, and categorical assignment statements and to predicates, ESP assigns scores to numeric assignment statements and to predicates, and NUMFL assigns scores to each subexpression of numeric assignment statements.
Predicate Switching assigns scores only to predicates. Baah et al's linear regression technique [1]} and the other coverage-based SFL techniques assign scores to all the statements, although each statement within a control dependence region receives the same score. To enable a fair comparison between techniques, we confined the comparison to only predicates and numeric assignment statements. (Note that to reduce overhead in this study only the faulty classes are instrumented.) With Predicate Switching, however, we reported the cost of finding the nearest predicate to the fault, since the technique does not assign scores to non-predicates. As a result of these restrictions, our study did not evaluate UniVal's ability to handle string variables. We intend to do so in a future study.
